Semiconductor wafers may be inspected for defects such as, e.g., surface imperfections, particles, irregularities in the thickness of thin film coatings, and the like, which may hamper the performance of the semiconductor wafers. Some existing inspection systems direct a beam of radiation on the surface of the semiconductor wafers, then collect and analyze light reflected and/or scattered from the surface to quantify characteristics of the surface.
Traditionally, the wafer edge has been of secondary concern to semiconductor manufactures, since it was considered a non-active area. However, there is a growing industry awareness that wafer edge conditions impact yields, directly and indirectly. For instance, a large scratch, residual slurry or open blister on the bevel can flake or peel off, depositing particles on the front surface that cause the defects. Therefore, additional inspection tools and techniques are desirable to inspect the edge or near edge of semiconductor wafers, compound semiconductor wafers, transparent wafers or thin film disks for defects such as particles, scratches, pits, mounds, cracks, blisters, missing films, chips, and other defects. However, most current inspection tools are macro inspection tools and the inspection techniques include an inspection on the front surface first, manually inspecting the wafer edge with a microscope and comparing density of edge defects to behavior on front surface. The current inspection tools and techniques are time consuming and require a large number of standard samples, which decreases the throughput in semiconductor manufacture.
It is within this context that embodiments of the present invention arise.